Hi-

We pickle ferrous wire at one stage of our process in sulfuric acid. What is the industry standard method for controlling a Sulfuric Acid pickeling bath (target is 5-7%). I've heard titration is the best way, but I wonder if a digital pH meter or a refractometer reading would suffice. I think the later two may have drawbacks - for example the refractometer would probably pick up the Iron in solution as well, and give a false reading.

Also, where can I buy a titration kit for Sulfuric acid?

Thanks for any help.

Chris

HI Chris,
This is a good question. I have tried using a digital PH meter but it does not work. I've tried it. Of course it will give you a very low PH reading but it will not tell you what percentage sulfuric acid you have.
Titration. Never used it.

I have found that the best way for our applications were to use a hydrometer.

I wonder why the Hydrometer reading would be more accurate than Refractometer. It seems to me that both would pick up the Iron in solution and thus be thrown off. On the other hand I'm not sure what the best measure of how much life is left in a pickeling bath is - pH and Titration each seem to have their own drawbacks. I wish my Chemistry class wasn't so long ago...

Anyone else have a method they trust?

Although I don't use Sulfuric Acid, I do use Hydrofluoric and Nitric Acids...among other chemicals for my product. As with all my chemicals I titrate twice daily as well as use the PH meter. For accurate results I don't see you going past titration. A PH meter will give you an indication but will not give you an accurate concentration of your chemical to ensure optimum results as well as ensure you're not using too much chemical. I am sorry but I have never used a refractometer so I can not comment.
Your supplier of chemical should supply the titration method along with your MSDS's. Titration kits are really just basic chemist gear and can be bought in many places (a local lab equip supplier or equip specialist). Your chemical supplier should also be able to help you with this as they too should have titration equip.
If you are not getting much support from your supplier it may be worth looking at a more reputable one for your future needs. A good chemical supplier will normally titrate with you at least once per 3 months.